Starfish?

[RedReefer777]

Hey everyone!
So I bought a really cool small piece of live rock the other day filled with some macro algea, some orange sponges, got a few mini snails out of it but I found these the other day and have no idea what they are, there four of them in a small area and I dont seem to see any others...any help would be appreciated thank you!

 

[Crabs McJones]

Medusae hydroid. Generally harmless, tend to die out over time

 

[Lovemyreef2015]

I agree with above^^ no need to worry